Nuclear power plants and other nuclear facilities typically store fuel rods or other radioactive materials in large pools of water. These water pools provide both cooling and shielding for the radioactive materials. Typically, such pools use a centralized water purification system which is permanently mounted in a dry equipment or auxiliary room. Because such systems concentrate radioactive contaminants which are present in the pool water, high radiation areas develop which significantly increase personnel exposure during required periodic operation and maintenance.
An alternative to these types of systems which was used in the past consisted of submersible concrete vaults which contained six 6.3 cubic foot resin tanks connected in parallel with the flow provided by a 2.5 horsepower submersible pump. Such a system produced a minimal flow rate (50 to 60 GPM), required excessive floor space (22.3 square feet), and produced excessive radioactive waste due to the integral concrete shield vault (waste packaged volume to expended resin volume ratio of 4.1:1). Such systems were also difficult to dispose of due to the high levels of radioactive contamination built up on the rough concrete surfaces.
A method and apparatus for purifying fluids containing radioactive impurities is disclosed in U.S. Pat. No. 4,107,044 (Levendusky). This apparatus includes a vessel having appropriate radiation shielding thereabout. Inside the vessel is a means for the filtration of undissolved solids and ion exchange removal of dissolved solids. The radioactive shielding is designed to be sufficient to preclude the emission of radiation from within the vessel upon the complete expenditure of the filter apparatus and demineralizing material. The apparatus is designed to be portable in order to be brought to a plant, utilized, and then carted away for disposal.
Other water purification systems have also been disclosed in the prior art. For example, in U.S. Pat. No. 3,276,458, (Iverson et al) an ultra pure water recirculating system including a filter, an ultra violet lamp sterilizer and an ion exchange resin in the circulating system is disclosed. A similar system which produces hydrogen-free water by the addition of ozone is also disclosed in U.S. Pat. No. 4,548,716 (Boeve).
A process for decontaminating water, and in particular for removing fission products and other radioisotopes from radioactively contaminated water, is disclosed in U.S. Pat. No. 2,752,309 (Emmons et al). In this process, the water is fed through a first column including a layer of glass wool, a layer of steel wool, a layer of burned clay, and a layer of moist activated carbon. Then, the water is fed through a second column containing an anion exchange resin and a cation exchange resin. An apparatus which utilizes ultraviolet radiation in the purification of water is also disclosed in U.S. Pat. No. 4,438,337 (Forrat).